This invention relates to a method for making one or more operative, optical surfaces to form part or parts of optical devices in a body of material. For the purpose of illustration herein, preferred manners of practicing the invention are described in conjunction with the making of semiconductor diode lasers, a field wherein the steps of the invention offer significant utility.
At the present time, substantially all commercially available semiconductor diode lasers are created by cleaving dice from wafers of optical semiconductor material, with the cleaved facets serving as the operative laser mirrors (optical surfaces). Many other processes have been proposed in the past for preparing such mirrors, including wet chemical etching, reactive ion etching (dry etching), and chemical etching with subsequent mass-transport. All of these prior techniques present certain difficulties which those skilled in the art would like to avoid. For example, some involve complex photolithographic masking procedures where masking or related errors can result in a poor yield of devices. Such poor-yield characteristics substantially rule out these procedures for the making of a monolithic multiple-device integrated unit. Lasers prepared by cleaving do not lend themselves, practically, to the coupling of such lasers to create complex monolithic topographies.
Accordingly, a general object of the present invention is to provide a new and very effective technique for preparing optical surfaces, such as mirror facets, in optical devices, such as semiconductor lasers, which avoids the problems that shadow many prior art techniques.
More particularly, an object of the invention is to provide a novel procedure which avoids completely complex steps, such as photolithographic masking steps, and which also permits the simple formation of complex monolithic architectures.
According to a preferred manner of practicing the invention with regard to semiconductor material, a wafer of optical semiconductor material is positioned so that a selected face in the wafer is disposed appropriately in a predetermined work zone. Such accomplished, a focused ion beam is directed in a selected manner, typically under the control of a computer, to impinge the selected face in the wafer thereby to remove material to create the desired optical surface.
By employing this same technique through plural selected directions of such an ion beam, plural optical devices, which couple appropriately with one another in a complex architecture, can easily be laid out monolithically on a single, unitary wafer.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.